In recent years, the need of reducing electromagnetic wave interference (EMI) has heightened due to increasing usage of electronic devices. It has been pointed out that EMI causes malfunctions and failures of electronic and electrical devices, and is also hazardous to humans. For this reason, with respect to electronic devices, it is required that the strength of electromagnetic wave emission is controlled within the range of governmental standards or regulations.
Specifically, plasma display panel (PDP) generates electromagnetic waves in principle because it is based on the principle that rare gases are converted to a plasma state to emit ultraviolet rays stimulating phosphor to emit light. Further, since near-infrared rays are also emitted at this time, resulting in malfunction of operational devices, such as remote controls, so that near-infrared shielding capability as well as electromagnetic wave shielding capability has been desirable. Electromagnetic wave shielding capability is simply represented as a surface resistance value, and in the light-transmitting electromagnetic wave shielding material for a PDP, required is a value of less than 10Ω/sq., and in a consumer plasma television using a PDP, the required value is less than 2 Ω/sq., and the very high conductivity of less than 0.2 Ω/sq. is more desirable.
Further, the desired level of near-infrared ray shielding is at least 60% to be cut off, and preferably at least 80% to be cut off, and still higher shielding capability is expected.
Furthermore, in order to enhance a PDP function, addition of mechanical strength to a PDP body of a thin film of glass, antireflection of sunlight, and color tone correction are desired in addition to near-infrared absorbability.
For this reason, plural transparent base plates are adhered to add mechanical strength, for which employed are combinations of layers, such as a conductive layer for electromagnetic wave shielding, a near-infrared absorption layer for near-infrared shielding, an antireflection layer for antireflection of sunlight, and a layer containing a dye for absorption in a visible light region.
To solve the above problems, specifically to solve the problems of electromagnetic wave shielding and a near-infrared ray, proposed have been methods satisfying both of an electromagnetic wave shielding property utilizing a metal mesh having apertures and a shielding property employing a near-infrared absorption dye. For example, one method is to adhere an infrared absorption film onto a glass plate into the surface of which a metal mesh having a high aperture ratio has been burned. However, in this method, the manufacturing process of burning a metallic mesh is complicated and complex, resulting in problems of a high level of skill in manufacturing and a long processing time.
On the other hand, since the developed silver obtained from silver halide grains is metallic silver, it is possible to produce a mesh of gold or silver depending on the manufacturing method. For example, if a photosensitive material containing silver halide grains is exposed via a mesh and photo-processed, the conductive metallic silver layers in which silver grains gathered in the shape of the mesh can be formed. Since a binder fills the spaces among the silver grains, resulting in interference of conductivity, it is necessary to reduce the binder volume, but conductivity is not sufficiently improved only by it. Therefore, methods employing plating treatment to enhance conductivity are proposed, (please refer to, for example, Patent Documents 1 and 2). However, the manufacturing process of a plating treatment needs to employ a plating solution with the inherent problem of generating harmful effluent containing heavy metals.
(Patent Document 1) Japanese Patent O.P.I. Publication No. 2004-221564
(Patent Document 2) Japanese Patent O.P.I. Publication No. 2004-221565